Make getNetworkSpecifier() public API.

The builder lets clients set it, and this may be useful for
unit tests of apps. It should be public.
The need arises from uses of this in WiFi and Telephony
network factories.

Test: build
Bug: 135998869
Change-Id: I57279cac139c28e8654d2066ba0c60edd1e6cd98

core/java/android/net/NetworkRequest.java

@@ -17,6 +17,7 @@
 package android.net;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
 import android.annotation.SystemApi;
 import android.annotation.UnsupportedAppUsage;
@@ -461,6 +462,14 @@ public class NetworkRequest implements Parcelable {
         return networkCapabilities.hasTransport(transportType);
     }
 
+    /**
+     * @see Builder#setNetworkSpecifier(NetworkSpecifier)
+     */
+    @Nullable
+    public NetworkSpecifier getNetworkSpecifier() {
+        return networkCapabilities.getNetworkSpecifier();
+    }
+
     public String toString() {
         return "NetworkRequest [ " + type + " id=" + requestId +
                 (legacyType != ConnectivityManager.TYPE_NONE ? ", legacyType=" + legacyType : "") +